“…CFCs in groundwater are now used regularly as transient tracers, and many successful applications of CFCs as transient tracers have been reported (e.g., Katz et al, 1995;Plummer et al, 1998a;Szabo et al, 1996). The conservativeness of CFCs is usually assumed in such applications (Happell et al, 2003), but the depletion of CFCs has been found in various environments, including aquifers (Cook et al, 1995;Happell et al, 2003;Hinsby et al, 2007;Horneman et al, 2008;Oster et al, 1996;Plummer et al, 1998aPlummer et al, , 1998bSebol et al, 2007), surface water (Happell et al, 2003;Oster et al, 1996), and marine water (Shapiro et al, 1997). Cook et al (1995) showed that the groundwater recharge rate estimated using CFC-113 (90 mm y À1 ) was smaller than the rate estimated using a 3 H bomb pulse (150 mm y À1 ) or CFC-12 (130 mm y À1 ) because of the sorption of CFC-113 to materials in the aquifer.…”